Temperature controlled showerhead for high temperature operations

ABSTRACT

A temperature controlled showerhead assembly for chemical vapor deposition (CVD) chambers enhances heat dissipation to provide accurate temperature control of the showerhead face plate and maintain temperatures substantially lower than surrounding components. Heat dissipates by conduction through a showerhead stem and removed by the heat exchanger mounted outside of the vacuum environment. Heat is supplied by a heating element inserted into the steam of the showerhead. Temperature is controlled using feedback supplied by a temperature sensor installed in the stem and in thermal contact with the face plate.

BACKGROUND

A Chemical Vapor Deposition (CVD) chamber typically includes ashowerhead with a perforated or porous planar surface to dispensereactants and carrier gases in a uniform manner over a second parallelplanar surface, such as a semiconductor substrate surface. A substratemay be heated to a process temperature at which precursors reactresulting in a film deposited on the substrate surface. Showerheadreactors, or parallel-plate reactors, lend themselves to implementationof plasma-enhanced processes, e.g., plasma-enhanced chemical vapordeposition (PECVD). A substrate support (e.g., a pedestal) may begrounded and used as one of the electrodes. A showerhead may be used asanother electrode, to which RF power is applied. In anotherconfiguration, RF power may be applied to the substrate support, whilethe showerhead may be grounded.

Deposition uniformity may be negatively affected by variations inprocess parameters, such as temperatures of the substrate and theshowerhead. These variations may appear during process initiation (e.g.,before reaching steady state), cleaning cycles, and idling. For example,when a reactor is initially turned on, it may take long time before thetemperature of the showerhead is stabilized. The showerhead may beheated by radiation from the substrate (or the substrate pedestal) andby the plasma, which may be introduced at some point during processingcausing additional temperature fluctuation. At the same time, theshowerhead may loose some heat to the process gases flown through theshowerhead and due to radiation from its external surfaces. Further,temperature variation may be caused by other more permanent changes inthe system, such as drifts in surface emissivity of the showerhead.Variable temperature may cause substantial non-uniformity of thedeposited films. Furthermore, operating a showerhead at hightemperatures shortens its operating life and leads to particlecontamination. For example, temperatures above 300° C. can result inrapid formation of aluminum fluoride on an aluminum showerhead surface.The aluminum fluoride tends to flake off and fall onto the substratebelow.

New apparatuses and methods are needed to more precisely controlshowerhead temperature and to operate showerheads at lower temperatures.

SUMMARY

A temperature controlled CVD showerhead with enhanced heat transferfeatures provides accurate and stable temperature control and reducestemperature fluctuations caused by variations in the chamber. Suchshowerhead is capable of quick recovery to the temperature set pointwhen changes in the operating environment perturb the system (e.g.,turning on a plasma generator, introducing a new substrate onto thepedestal, changing flow rates of process gases). Accurate temperaturecontrol improves substrate-to-substrate uniformity.

A temperature sensor is used to monitor the face plate temperature andto provide a feedback for controlling the heating element and/or theheat exchanger. Effective heat transfer paths exist between the faceplate and the heating element as well as between the face plate and theheat exchanger allowing for efficient heat supply or removal from theface plate. Heat transfer characteristics are driven by largecross-sectional profiles of the back plate and the stem. Further,materials having high thermal conductivity, such as aluminum 6061-T6,are used for construction of the elements. Heat transfer is driven by atemperature gradient established by passing high thermal capacitycooling fluids through the heat exchanger and high power heatingelements installed in the stem.

Heat transfer and dissipation characteristics coupled with accuratetemperature control allow operating a showerhead at temperaturessubstantially lower (e.g., between about 100° C. and 300° C.) than thetemperature of the nearby pedestal despite substantial heat flux fromthe pedestal to the face plate. Lower temperatures extend the operatinglifetime of the showerhead and minimize particle contamination. Incertain embodiments, heat dissipation is also a result of providing highemissivity external surfaces on the back plate and the stem.

A heating element, a heat exchanger, and a temperature sensor can beeasily removed from the showerhead. In certain embodiments, thesecomponents can be replaced without impacting the internal environment ofthe deposition chamber. In other words, the deposition chamber may bemaintained at a low operating pressure while one or more of theabovementioned showerhead assembly components are replaced. Removablecomponents simplify troubleshooting and maintenance of the showerheadand the overall deposition system and minimizes its downtime.

In certain embodiments, a temperature controlled showerhead assembly foruse in a chemical vapor deposition (CVD) apparatus includes a heatconductive stem, a back plate attached to the heat conductive stem, aface plate thermally coupled to the heat conductive stem and attached tothe back plate, a heating element thermally coupled to the heatconductive stem, a heat exchanger thermally coupled to the heatconductive stem, and a temperature sensor thermally coupled to the faceplate. The temperature controlled showerhead may be configured tomaintain the temperature of the face plate within a predetermined rangeby providing heat transfer paths between the removable heating elementand the face plate and between the removable heat exchanger and the faceplate. The face plate may have multiple through holes configured foruniform distribution of process gases. In particular embodiments, aheating element, a heat exchanger, and/or a temperature sensor areremovable from the temperature controlled showerhead assembly.

A solid cross-section of the heat conductive stem may be at least about5 square inches on average along the length of the shaft portion. A heatconductive stem, a back plate, and/or a face plate may be made of amaterial with a thermal conductivity of at least about 150 Watts permeter per Kelvin. In particular embodiments, a heat conductive stem, aback plate, and/or a face plate are made of aluminum 6061 and aluminum3003. An average thickness of the back plate may be at least about 2inches, while an average thickness of the face plate is between about0.5 inches and 1 inch. An average gap between the face plate and theback plate may be between about 0.25 inch and 0.75 inch. A contact areabetween the face plate and the back plate may be between about 30 squareinches and 50 square inches. A face plate may have a diameter of betweenabout 13.5 inches and 16.5 inches.

In certain embodiments, a heat exchanger includes a convective coolingfluid passageway configured to allow for a flow of a cooling fluid. Thecooling fluid may be water or a liquid antifreeze solution. In the sameor other embodiments, a heat exchanger is positioned within about 7inches from the face plate. A temperature controlled showerhead assemblymay be configured to maintain the temperature of the face place atbetween about 200° C. and 300° C. for an emissivity of the face plate atbetween about 0.2 and 0.8. In certain embodiments, a heating elementincludes two cartridge heaters each configured to provide power outputof at least about 500 W.

A stem may include a top surface. A heating element may be positionedwithin the stem and configured to be placed into the stem and removedfrom the stem through the top surface. Further, a temperature sensor maybe positioned within the stem and configured to be placed into the stemand removed from the stem through the top surface.

In certain embodiments, an external surface a stem and/or a back platehas high emissivity. For examples, the high emissivity surface may beanodized aluminum.

In certain embodiments, a Chemical Vapor Deposition (CVD) system fordepositing a semiconductor material on a partially manufacturedsemiconductor substrate includes a processing chamber configured tomaintain a low pressure environment within the processing chamber, asubstrate support for holding the partially manufactured semiconductorsubstrate and maintaining a temperature of the partially manufacturedsemiconductor substrate at between about 500° C. and 600° C., and atemperature controlled showerhead assembly. The temperature controlshowerhead assembly may further include a heat conductive stem, a backplate attached to the heat conductive stem, a face plate thermallycoupled to the heat conductive stem and attached to the back plate, aheating element thermally coupled to the heat conductive stem, a heatexchanger thermally coupled to the heat conductive stem, and atemperature sensor thermally coupled to the face plate. The temperaturecontrolled showerhead is configured to maintain the temperature of theface place within a predetermined range by providing heat transfer pathsbetween the heating element and the face plate and between the heatexchanger and the face place. The face plate of the temperaturecontrolled showerhead may be positioned within about 0.7 inches from thesubstrate support. The temperature controlled showerhead may beconfigured to maintain the temperature of the face plate at betweenabout 200° C. and 300° C. while the substrate support is maintained atbetween about 500° C. and 550° C. In certain embodiments, a CVD systemalso includes an in-situ plasma generator.

In certain embodiments, a CVD system is a single-station depositionsystem. In other embodiments, a CVD system includes a second substratesupport. The first substrate support and the second substrate supportmay be positioned inside the same processing chamber and configured tobe exposed to the same environment. In other embodiments, a CVD systemalso includes a second processing chamber configured to maintain adifferent environment. The first and second substrate supports may bepositioned in different processing chambers (e.g., the first processingchamber and the second processing chamber).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of showerhead temperatures in a four station chamberover time.

FIG. 2A is a graph of silicon nitride spacer thickness deposited atvarious showerhead temperatures.

FIG. 2B is a graph of film stress for silicon nitride spacer depositedat various showerhead temperatures.

FIG. 3A is a cross-sectional view of the temperature controlledshowerhead in accordance with certain embodiments.

FIG. 3B is a top view of the temperature controlled showerhead inaccordance with certain embodiments.

FIG. 4A is a cross-sectional view of the face plate in accordance withcertain embodiments.

FIG. 4B is a bottom view of the face plate in accordance with certainembodiments.

FIG. 5 is a schematic view of the temperature controlled showerheadassembly in accordance with certain embodiments.

FIG. 6 is a schematic of one embodiment of RF filters used to reduce oreliminate RF noise in accordance with certain embodiments.

FIG. 7 is a schematic view of a system in accordance with certainembodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail to not unnecessarily obscure the present invention.While the invention will be described in conjunction with the specificembodiments, it will be understood that it is not intended to limit theinvention to the embodiments.

In this application, the terms “substrate” and “wafer” will be usedinterchangeably. The following detailed description assumes theinvention is implemented on semiconductor processing equipment. However,the invention is not so limited. The apparatus may be utilized toprocess work pieces of various shapes, sizes, and materials. In additionto semiconductor wafers, other work pieces that may take advantage ofthis invention include various articles such as display face planesprinted circuit boards and the like.

Showerhead temperatures drift over time and affect deposition reactionrates and film properties. FIG. 1 is a graph of four showerheadtemperatures in a four station deposition chamber over a 50 wafer runwithout any temperature control, i.e., no heating or cooling applied tothe showerheads. The first station showerhead temperature corresponds toline 102. The second station showerhead temperature corresponds to line104. The third station showerhead temperature corresponds to line 106.And, finally, the fourth station showerhead temperature corresponds toline 108. Over time, the showerhead temperatures of the second, third,and fourth stations increased until they reached a steady statetemperature at about 3700 seconds. The plasma condition in the chamberis represented as a step function with line 110. Initially, the plasmawas provided in a dummy deposition mode to warm up the showerheads, andafter about 10 minutes the wafer processing began. In the first station,the temperature started to decrease gradually after wafer processingbegan because each incoming wafer (that is substantially colder than theshowerhead) at that station cools the chamber components, including theshowerhead, as the wafer is warmed up to the process temperature. Thus,the temperature profiles in the subsequent stations are progressivelyhigher. The second station showerhead was cooler than the third stationshowerhead because the incoming wafer to the second station was coolerthan the incoming wafer to the third station. For all stations, theshowerhead temperature reached an equilibrium temperature after sometime.

FIG. 1 illustrates that a substrate being processed in a multi-stationchamber would experience different showerhead temperatures at differentstations. The same problem appears in a typical single-station chamber.For example, a showerhead temperature can fluctuate while multiplesub-layers are deposited on that station. During deposition, heattransfer in the showerhead is a dynamic process impacted by a pedestaltemperature, plasma presence and its power, and other factors. If noteffectively controlled, a showerhead experiences substantial temperaturedeviations. In situations when a showerhead temperature impactsdeposited film properties, each layer deposited using a differentshowerhead on the same wafer may result in different properties. One CVDprocess example that is particularly sensitive to fluctuations inshowerhead temperature is deposition of silicon nitride spacers. Anothersuch example is deposition using a tetraethylorthosilicate (TEOS)precursor.

Differences in film properties resulting from different showerheadtemperatures are illustrated in the following two examples. FIG. 2Ashows a plot of film thicknesses deposited at different showerheadtemperatures. With all other process parameters kept constant, highershowerhead temperatures resulted in thicker films. Thus, a layerdeposited at the beginning of a wafer run (e.g., after some idle time orchamber cleaning and while the showerhead is still relatively cold)would be thinner than a layer deposited once the process reaches steadystate. FIG. 2B illustrates effects of the showerhead temperature onstress of a silicon nitride spacer film. As the showerhead temperatureincreases, the stress level decreases. Variations in stress level mayhave a negative impact on device performance (e.g., transistors).

A temperature controlled showerhead improves substrate-to-substrateuniformity both for bulk films and individual sub-layers insingle-station and multi-station apparatuses, increases throughput byeliminating non-processing delays (e.g., to stabilize temperature),reduces particle contamination by operating a showerhead at lowertemperatures, and allows for better control of various film properties.In certain configurations, more precise control ensures that multipleshowerheads in the chamber are operated with substantially similarprocess parameters and close to the target parameters. As a result, filmproperties of different sub-layers are better controlled.

Improving temperature control and providing more adequate heat paths maybe used to reduce thermal cycling of the showerhead. In other words, theshowerhead temperature may be maintained at comparable levels duringdeposition, idling, and/or cleaning. The reduction in thermal cyclingincreases processing throughput (by minimizing or eliminatingtemperature ramp-up and stabilization periods) and helps to reduceparticle contamination caused by flaking of deposits on the surface ofthe showerhead. Deposits on the surface of the showerhead have differentthermal expansion coefficients than the materials of the showerhead,resulting in flaking of the deposits during thermal cycling.

Particle contamination may also be reduced by lowering operatingtemperatures of the showerhead. Even though substrates are processed atabout 400° C.-600° C. in close proximity to the showerhead, effectiveheat transfer coupled with heat dissipation allows maintaining the faceplate of the showerhead at between about 200° C. and 300° C. It shouldbe noted that for the purposes of this document showerhead temperaturereferences are provided for the face plate unless otherwise stated. Heatis removed by transferring it from the face plate through the back plateand the stem to a heat exchanger, by radiation from the back plate,and/or a combination thereof. In addition to reduction of particlecontamination, certain CVD processes require lower showerheadtemperatures to achieve certain film properties. For example, loweringshowerhead temperature improves stress levels in certain films, asevidenced by FIG. 2B.

In general, there are two main types of CVD showerheads: a chandeliertype and a flush mount type. A chandelier type showerhead has a stemattached to the top of the chamber on one end and a face plate on theother end. A part of the stem may protrude from the chamber top forconnecting gas lines and RF power. A flush mount showerhead type isintegrated into the top of a chamber and typically does not have a stem.This document generally refers to the chandelier type of showerheads,however it should be understood that certain features could be used inflush mount showerheads as well, as would be readily understood to oneof skill in the art given the description provided herein.

Showerhead temperature changes when heat is added or removed. Some ofthis heat is added or removed in a controllable fashion, e.g., based ona current registered temperature and a set point. Various components ofthe showerhead further described below enable this controllable process.However, some heat is transferred due to changes in surroundingconditions and this transfer has to be compensated for in order tomaintain a stable temperature. For example, heat is added to theshowerhead when the plasma is turned on due to the collision of chargedparticles with the showerhead. Furthermore, the showerhead may be heatedby other surrounding components, such as a processed wafer or apedestal. The showerhead looses heat when colder materials areintroduced into the chamber, e.g., reactant gases supplied through theshowerhead or a substrate introduced from a load-lock or another colderstation. Further, heat is lost due to conduction to other chambercomponents (e.g., through the showerhead stem material to the chamberceiling) and radiation (e.g., from the back plate).

FIG. 3A is a schematic cross-sectional view of a temperature controlledshowerhead 300 in accordance with certain embodiments of the invention.A showerhead 300 may be a part of the showerhead assembly furtherdescribed in the context of FIG. 5 and a part of the deposition systemfurther described in the context of FIG. 7. The showerhead 300 includesa heat conductive stem 304, a back plate 306, and a face plate 308. Thestem 304 and the back plate 306 may be separate mechanical components orintegrated into a single body. In a similar manner, the back plate 306and the face plate 308 may be separate mechanical components orintegrated into a single body. For example, two or more of thesecomponents may be manufactured together from a single block of materialor attached together after the fabrication (e.g., welded, pressed, fusedtogether) in such a way that these components cannot be easilyseparated. The latter approach may provide for better heat transferbetween integrated components. However, removably attached componentsmay be preferable in embodiments where one or more components may needto be periodically changed. For example, a face plate 308 may beremovably attached to the back plate 306 to allowing for servicing of amanifold area 316, to replace a face plate 308 when one wears out, or toreplace a face plate 308 with another one having a differentdistribution pattern (e.g., a hole pattern on the bottom surface furtherdescribed in the context of FIG. 4B). In a similar manner, the backplate 306 may be removably attached to the face plate 308 and/or to thestem 304. In certain embodiments, a back plate 306 may be replaced witha different back plate that has different thermal transfercharacteristics.

In certain embodiments, the stem 304 has a cylindrical shape with anaverage diameter (D_(STEM) as shown in FIG. 3A) of between about 2inches and 4 inches or, more specifically, between about 2.5 inches and3.5 inches or, even more specifically, between about 2.75 inches and3.25 inches. It should be noted that dimensions presented in thisdocument correspond to a showerhead configured for processing 300-mmwafers, unless otherwise noted. It should be understood that otherdimensions may be used for showerheads configured to process differentsubstrate types and sizes (e.g., 200-mm wafers, 450-mm wafers, etc.).

Another way of characterizing the stem 304 is based on its solidcross-sectional area (i.e., a cross-section material surface thatexcludes any openings). In certain embodiments, such cross-sectional ison average between about 3 square inches and 10 square inches or, morespecifically between about 4 square inches and 8 square inches. Theheight of the stem 304 (H_(STEM) as shown in FIG. 3A) may be on averagebetween about 1 inch and 5 inches or, more specifically, between about 2inches and 4 inches or, even more specifically, between about 2.5 inchesand 3.5 inches.

However, the length of the stem may be less relevant for a thermalanalysis than, for example, the distance to a heat exchanger thermallycoupled to the stem as discussed in the context of FIG. 5. Further, anyfeatures provided in the stem, such as a process gas feed opening 310, atemperature sensor opening 312, and a heating element opening 314 shouldbe accounted for when analyzing heat conductivity of the stem. Otherthermal analysis considerations include thermal properties of thematerials used for stem construction (e.g., heat conductivity, heatcapacity), a temperature gradient, thermal coupling to other elements(e.g., a heat exchanger, a back plate), and others.

The back plate 306 may also have a cylindrical shape. In certainembodiments, the back plate 306 may be characterized as a stack of disksas shown in FIGS. 3A and 3B. For example, a stack may include two,three, four, five, or more disks. In particular embodiments, the backplate is a stack of three disks. The largest disk, which is typicallypositioned at the bottom of the stack and in the contact with the faceplate 308, may have a diameter (not referenced in the drawings) ofbetween about 12 inches and 14 inches and a thickness (not referenced inthe drawings) of between about 0.5 inches and 1 inch. Another disk maybe between about 0.5 inches and 1.5 inches smaller in diameter (D2_(BACK PLATE) in FIG. 3B) than the largest disk and have a thickness (H2_(BACK PLATE) in FIG. 3A) of between about 0.5 inches and 1 inch. Yetanother cylinder may be between about 2.0 inches and 4.0 inches smallerin diameter (D1 _(BACK PLATE) in FIG. 3B) than the largest cylinder andhave a thickness (H1 _(BACK PLATE) in FIG. 3A) of between about 1.0 and2.0 inches.

Generally, various disk stacks described above form a single unifiedbody (e.g., fabricated from a single block of material or permanentlyattached together using welding, pressing, fusing, or other techniques).In certain embodiments, each disk may be a separate component that canbe stacked together with other disks of the same or different sizes in amodular fashion to form a back plate. The number and size of the disksmay be selected based on the heat transfer requirements and may bereconfigured into another stack for different requirements.

The face plate 308 may be slightly larger than the substrate, forexample, between about 100% and 125% larger that the substrate orbetween about 14 inches and 16 inches in diameter (D_(FRONT PLATE) inFIG. 3B) for a 300-mm wafer showerhead type. To ensure thermaluniformity throughout the face plate 308 and to conduct heat to and fromthe back plate 306, the face plate may have a thickness (T_(FRONT PLATE)in FIG. 3A) of at least about 0.5 inches or, more specifically, betweenabout 0.5 inches and 1 inch or, even more specifically, between about0.7 inches and 0.8 inches. Further, a combination of the front plate 308and the back plate 306 may be characterized by a contact area betweenthe two, which, in certain embodiments, may be between about 10 squareinches and 30 square inches or, more specifically, between about 15square inches and 25 square inches. As shown in FIGS. 3A-B, the contactarea may be shaped as a ring with a diameter of between about 12 inchesand 16 inches and a cross-section of between about 0.25 inches and 1inch.

Showerhead components described above may be fabricated from materialsthat are capable of operating in environments (e.g., fluoride basedchemicals, plasma) and conditions (e.g., temperatures of up to about600° C.) of a typical CVD chamber. Examples of materials includealuminum (e.g., grade 6061-T6, 3003-O, 3003-H12), stainless steel, andceramics (e.g., alumina).

Process gases are introduced through a gas feed channel 310 in the stem304 and flow through the back plate 306 before entering the manifoldarea 316 between the back plate 306 and the face plate 308. The manifoldarea 316 may include a baffle (not shown) for distributing the processgases evenly throughout the area 316. The gap between the back plate 306and the face plate 308 may be on average between about 0.25 inches and 1inch.

To maintain uniform gas flow in the manifold area 316, the gap may bekept constant with a number of separator/spacers positioned between theback plate 306 and the face plate 308 at various locations, e.g. 3, 6,or up to 10 locations. In certain embodiments, as shown in FIG. 4A,separator/spacers 402 are a part of the face plate 308. The back plate306 may be attached through separator/spacers 402 to the face plate 308by means of welding, or brazing. Alternatively, the back plate 306 maybe fastened through separator/spacers to the face plate 308 at threadedblind holes (not shown) In other embodiments, variously shaped spacersor bushings with or without internal threads may be used. Although thescrews are described to enter the back plate 306 and to thread into theface plate 308, the reverse configuration may be used (i.e., enteringthrough the face plate 308 and threading into the back plate 306).

Returning to FIGS. 3A and 3B, the stem 304 may also include an openingfor inserting a temperature sensor, i.e., a temperature sensorthermo-well. The opening 312 may be sealed away from the manifold area316 to prevent process gases from escaping through the opening 312. Theopening 312 may allow replacing a temperature sensor withoutdisassembling the showerhead 300. In certain embodiments, a temperaturesensor could be replaced while the showerhead 300 is attached to adeposition chamber maintained at its operating pressures.

The temperature sensor opening 312 is configured in such a way that aninstalled sensor (element 506 in FIG. 5; not shown in FIGS. 3A and 3B)is thermally coupled with the face plate 308. For example, a back plate306 may have a feature extending into the manifold area 316 thatestablishes a more direct contact with the face plate 308 than, forexample, through the contact area around the perimeter of the showerhead300. In this configuration, a temperature sensor provides a fastresponse about the current temperature of the face plate and allowsmodifying the heat flux through the showerhead.

The stem 304 may also have one or more opening for inserting heatingelements, i.e., the heating element opening 314 as illustrated in FIGS.3A and 3B. This opening 314 is sealed from the manifold area 316. When aheating element (element 504 in FIG. 5; not shown in FIGS. 3A and 3B) isinstalled into the opening 314, it becomes thermally coupled with thestem 304 and/or the back plate 306. Thermal coupling of the heatingelement to the face plate 308 is established through the stem 304 andthe back plate 306. In certain embodiments, a heating opening 314 isconfigured to accommodate a cartridge heater. For example, an opening314 may have a diameter of between about 0.25 inches and 0.5 inches or,more specifically, between about 0.35 inches and 0.4 inches, and a depthof between about 3 inches and 7 inches or, more specifically, betweenabout 4 inches and 6 inches.

FIG. 4B illustrates a bottom view of the face plate 308 in accordancewith certain embodiments. The face plate 308 has a plurality of holes orperforations 406 to provide even distribution of process gases from themanifold area 316 into the deposition chamber. A particular example ofsuch holes is shown in FIG. 4B. The through holes may be machined,milled, or drilled, for example. Each hole may be between about 0.01inches and 0.25 inches in diameter or, more specifically, between about0.02 inches and 0.1 inches. In particular embodiments, a diameter of theholes 406 is about 0.04 inch in diameter. Some holes may have differentsizes than others. For example, hole sizes may increase further awayfrom the gas feed line 310. The number of holes may be between about 100and 10,000 or, more specifically between about 1,000 and 5,000. Inparticular embodiments, the number of holes is between about 3,750 and4,000. The holes may be distributed evenly throughout the face plate 308in various patterns, e.g., a honey comb pattern or increasingly largercircles. In particular embodiments, a number of circles that establishesthe pattern is between about 5 and 50 circles or, more specifically,between about 20 and 40 circles or, even more specifically, betweenabout 25 and 30 circles. For example, one hole may be in the center,followed by 6-15 holes positioned at the same distance from the centerhole (i.e., a circular pattern), followed by another 12-30 holespositioned also at the same distance from the center hole, but thissecond distance is twice the first distance, and so on. In certainembodiments, the first distance is between about 0.20 inches and 0.30inches. Further, holes 406 may form various patterns with unevendistribution, such as being more densely packed around the edges than inthe middle of the face plate or vice versa. Generally, distribution ofthe holes 406 in the face plate 308 depends on various factors, such asdesired film uniformity, film profile, and process gas parameters (e.g.,viscosity, flow rate).

In some embodiments, the face plate 308 is removably attached to theback plate 306 such that the face plate 308 can be changed due to end oflife, or to provide a new hole pattern. The back surface of the faceplate 308 may include mating features to attach and detach from the backplate 306. For example, one suitable mating feature may be a groove andthreaded blind holes. According to this example, the groove may mateonto a corresponding lip on the back plate 306. Screw holes on the backplate 306 or face plate 308 are positioned circumferentially and matchholes on the mating plate. Screws attach the back plate 306 and faceplate 308 together. The number of circumferentially positioned screwsmay be at least about 4, at least about 10, at least about 24, or atleast about 50. Other mating features for the back plate 306 and theface plate 308 may be used. For example, other fastening mechanisms mayinclude straps or clips or a simple friction based engagement may beused where the dimensions of the face plate 308 closely matches those ofa corresponding receptacle in the back plate 306. Additional details ofattaching the face plate to the back plate are described in U.S. patentapplication Ser. No. 12/181,927 filed on Jul. 29, 2008 incorporatedherein by reference in its entirety for purpose of describing face placeattachment. In certain other embodiments, the face plate 308 is notremovable from the back plate 306. For example, the two elements may befabricated from the same block of material or integrated together afterfabrication (e.g., welded, fused, pressed). The permanent attachmentbetween the face plate 308 and the back plate 306 may provide enhancedheat transfer between the two components.

FIG. 5 illustrates a temperature controlled showerhead assembly 500 inaccordance with certain embodiments. In addition to the showerhead thatincludes a stem 304, a back plate 306, and a face plate 308 describedabove, the assembly 500 may also include a heating element 504, a heatexchanger 502, and a temperature sensor 506. Any one of these elementsmay be removable.

A heating element 504 is thermally coupled to the stem 304 and/or theback plate 306. In certain embodiments, the heating element 504 is oneor more cartridge heaters positioned within heating element opening(s)of the stem. For example, two cartridge heaters may be used with acombined power output of between about 250 W and 2,500 W or, morespecifically, between about 500 W and 1,500 W. In certain embodiments,the heating element includes RF insulation, for example, by using anEMI/RFI filter or any other commercially available RF isolation device.

As shown in FIG. 5, a thermocouple 506 may be inserted through theopening in the stem 304 and extend through the back plate 306. Incertain embodiments, an entire temperature sensor opening 312 ismachined from the same block of material. It has been found in someembodiments that welding or otherwise integrating separate pieces of athermocouple well is prone to cracking during thermal cycling of theshowerhead and may result in vacuum leaks and/or malfunction of thethermocouple possibly resulting in thermal runaway of the system. Athermocouple 506 may be between about 0.05 inches and 0.25 inches indiameter on average or, more specifically, between about 0.10 inches and0.20 inches. The length of the thermocouple is determined by the designof the stem 304 and the back plate 306 and typically allows thethermocouple to extend all the way to the bottom of the opening 312 (seeFIG. 3A). In certain embodiments, the thermocouple 506 is between about4 inches and 8 inches in length or, more specifically, between about 6inches and 7 inches in length. Another example of a temperature sensingdevice that may be used instead of the thermocouple 506 is a non-contacttemperature sensor (e.g., pyrometry, fluorescence-based thermometry orinfrared thermometry).

The thermocouple 506 may also be insulated and isolated from the RF. TheRF isolation may be accomplished through operating an RF trap at onefrequency and an RF filter at another frequency. Typically, the RFapplied in a PECVD operation has two frequency components, a highfrequency (e.g., 13.56 MHz) trap and a low frequency (e.g., 400 kHz)one. The RF isolation device may include one or more filters. In oneembodiment, the RF isolation device includes a high frequency and a lowfrequency filter. Without RF isolation, it is believed that thethermocouple measurement would not be useful because the RF interferencefrom the plasma generator would be too great.

A schematic of a possible configuration of the RF isolation device isshown in FIG. 6. The thermocouple 506/601 is surrounded by a stainlesssteel sheath. This sheath is wound to a coil 603 in parallel to acapacitor 605. The coil acts as an inductor and the capacitor forms atank circuit which blocks the 13.56 MHz signal. The coil may have aninductance of about 1 microhenry, and capacitor 605 may have acapacitance of about 85 pf (picofarads). Remaining 13.56 MHz RF isshorted to ground 609 with the second capacitor 607, which may have acapacitance of about 10000 pf. Trapping the high frequency with thesheath also blocks the RF in the thermocouple wires embedded in thissheath. The 400 kHz frequency is not blocked by the 603/605 filter anddue to its lower frequency not shorted to ground by the capacitor 607.So at the end of the 13.56 MHz filter there is still 400 kHz noise thatis subsequently filtered out by the low frequency filter 611. In onedesign, the low frequency filter may be a two-stage low pass filter.Both stages may be a LC design similar to the high frequency filter.Please note that the low frequency filter may be connected directly tothe thermocouple wires, but the high frequency filter may be connectedto the sheath only.

Returning to FIG. 5, in order to maintain the face plate 308 attemperatures that are substantially lower than the substrate and thepedestal some heat sometimes needs to be removed from the face plate308. A heat path is provided between the face plate 308 and the heatexchanger 502 through the back plate 306 and the stem 304. The heatexchanger 502 is configured to remove from or, in certain embodiments,to deliver heat to stem 304. Further, some heat may be removed from theexposed surfaces of the back plate and the stem due to radiation. Eachof these heat removal features will now be discussed in more detail.

The heat exchanger 502 may be positioned on the stem 304 such that thetwo components are thermally coupled. For example, the heat exchanger502 and the stem 304 may have a contact surface (e.g., a heat exchangerforming a mounting surface at the top of the stem, or a sleeve aroundthe stem) of between about 20 cm² and 28 cm². The heat exchanger 502 maybe easily removed from the stem without impacting other components ofthe system or the environment of the deposition chamber.

The temperature in the heat exchanger 502 may be controlled bycirculating a cooling fluid through the heat exchanger 502. Examples ofcooling fluids include water, an antifreeze solution, and variouscooling gases (e.g., clean dry air (CDA), argon, helium, nitrogen,hydrogen, or a mixture of thereof). In particular embodiments, thecooling fluid is water supplied into the heat exchanger at between about15° C. and 30° C. at a flow rate of at least about 0.5 gallons perminute (GPM). It should be understood that the temperature of thecooling fluid and the flow rate can be adjusted to control the heat fluxbetween the heat exchanger 502 and the stem 304. In certain embodiments,the cooling fluid may be additionally cooled with an external chiller orheated with an external heater. Further, the valve 510 controlling theflow rate of the cooling fluid into the heat exchanger 502 may beadjusted to open or restrict the flow as described below.

In certain less demanding applications, the heat exchanger 502 alone maybe used to control the showerhead temperature (i.e., no heating elementsare provided in the stem). For example, a showerhead may be heated fromother external elements (e.g., a substrate) and the heat exchanger isused only to cool the showerhead down. In other embodiments, the heatexchanger may be configured to provide both heating and cooling bysupplying circulating fluid at various temperatures. In otherembodiments, the assembly includes one or more heating element 504 asdescribed above.

In addition to cooling provided by the heat exchanger, heat may radiateaway from the showerhead surfaces. To improve radiative cooling, theexternal surface of the stem and/or the showerhead may be coated with ahigh emissivity material. For example, the coating may be anodizedaluminum. The radiation is absorbed by the walls of the chamber that aregenerally much colder (e.g., around room temperature) than theshowerhead components. The chamber top may also be treated with a highemissivity material to increase radiative heat transfer. The insidesurface of the chamber top may be also coated with anodized aluminum,for example. The chamber top may be cooled independently, e.g., withcooling water lines.

In certain embodiments, the assembly 500 includes a temperaturecontroller 508. The controller 508 may be used to read the temperatureinformation from the thermocouple 506, and adjusts power delivered tothe heater 504 and/or flow rates of the cooling fluid through the heatexchanger 502. For example, if the controller 508 senses that thetemperature of the face plate 308 is substantially lower than the setpoint (e.g., the deposition chamber is being brought up to the operatingconditions), it may shut down (or close to a certain degree) the valve510 and increase the power supplied to the heater 504.

The controller 508 may also be connected to sensors measuring coolingfluid flow rates, temperatures of the cooling fluid when it entersand/or leaves the heat exchanger, and other process parameters. Forexample, the temperature controller 508 may also take feed forwardinformation. The feed forward information may be the time period untilthe plasma turns on. In some cases the feed forward information may alsoinclude other predictable events that affect the showerhead temperaturesuch as wafer processing with cold wafers or gas flow into theshowerhead. For example, the controller 508 may increase the heateroutput in anticipation of a cooling event, e.g., chamber purge, ordecrease the heater input in anticipation of a heating event, e.g.,plasma “on.” The controller 508 may also increase the cooling byincreasing cooling fluid flow in anticipation of a heating event ordecrease the cooling by decreasing cooling fluid flow in anticipation ofa cooling event.

Various combinations of the input and output components may be used indifferent controlling schemes. For example, active cooling (modulatingcooling fluid flow) may be used with active heating (heater in the backplate) to accurately control showerhead temperature. The showerheadtemperature may be measured directly from a thermocouple attached to theface plate, or determined indirectly from the exiting cooling fluidtemperature. In some cases, only active cooling or only active heatingmay be included in the control system. Still other inputs may beincluded, such as temperature sensing of the cooling fluid at the inletto accurately determine the heat removed from the showerhead.

FIG. 7 illustrates an example of a deposition system 700 in accordancewith certain embodiments of the invention. Examples of the system 700include a VECTOR Express™ system and a VECTOR Extreme™ system availablefrom Novellus Systems, Inc. in San Jose, Calif. Both of these systemsare also available in Ashable Hard Mask (AHM) configurations. It shouldbe noted that a novel showerhead described above could be used in CVDsystems without in-situ plasma (e.g., thermal CVD, remote plasmaenhanced CVD) and in CVD systems with in-situ plasma (e.g., PECVD,microwave plasma-assisted CVD). For brevity, a PECVD example isillustrated in FIG. 7 and described below. However, it should be notedthat the invention is not limited to this type of CVD system.

As shown, the system 700 includes a processing chamber 718, whichencloses other components of the system 700 and, in certain embodiments,serves to contain the plasma. The chamber 718 contains a showerhead 714and other process gas delivery hardware, a substrate pedestal 720, andsensors 724. An optional in-situ plasma generator 716, such aslow-frequency RF generator and/or a high-frequency RF generator, may beconnected to the showerhead 714 and/or pedestal 720. The power andfrequency are sufficient to generate a plasma from the process gas, forexample, 400-8000 W total energy for a deposition, and a higher powerfor a plasma anneal. In certain embodiments, the generators are not usedduring the deposition, e.g., the deposition takes place in “dark” ornon-plasma conditions. During the plasma anneal step, one or more HF, MFand LF generators may be used. For example, in a typical process, thehigh frequency RF component is generally between 2-60 MHz; in apreferred embodiment, the component is 13.56 MHz.

Within the processing chamber 718, the pedestal 720 supports a substrate721. The pedestal 720 typically includes a chuck, and lift pins to raiseand lower the substrate 721 during and between the deposition and/orplasma treatment reactions. The chuck may be an electrostatic chuck, amechanical chuck, a vacuum chuck or various other types of chuck as areavailable for use in the industry and/or research.

The process gases are introduced into the chamber 718 through theshowerhead 714 from one or more process gases source 702. The source 702may include valves and mass flow controllers (MFCs). It may becontrolled by a system controller 722 in such a way that desirableratios of the process gases' concentrations or partial pressures areachieved in the process chamber. Reaction products and other gases exitthe chamber 718 via an outlet 726. A vacuum pump (e.g., a one or twostage mechanical dry pump and/or a turbomolecular pump) typically drawsprocess gases out and maintains a suitably low pressure within theprocessing chamber by a closed loop-controlled flow restriction device,such as a throttle valve or a pendulum valve.

The chamber 718 may include a sensor 724 for sensing various processparameters, such as temperatures of the substrate 721 and the pedestal,chamber pressure, concentration of process gases inside the chamber, andothers. The sensor 724 may provide sensed information to the systemcontroller 722. Examples of the sensor 724 include residual gasanalyzers, pressure sensors, thermocouples, infrared pyrometers, andothers. It should be noted that other sensors may be included in theshowerhead 714 as described above.

In certain embodiments, a system controller 722 is employed to controlprocess parameters. The system controller 722 typically includes one ormore memory devices and one or more processors. The processor mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc. Typically there willbe a user interface associated with system controller 722. The userinterface may include a display screen, graphical software displays ofthe apparatus and/or process conditions, and user input devices such aspointing devices, keyboards, touch screens, microphones, etc. Althoughthe system controller 722 is shown connected to plasma generator 716,its placement and connectivity may vary based on the particularimplementation.

In certain embodiments, the system controller 722 incorporated some orall functions of the temperature controller described above (element 508in FIG. 5). For example, the system controller 722 may gatherinformation on temperature of the face plate and use this information toadjust heater output and/or flow through the heat exchanger. The systemcontroller 722 executes system control software including sets ofinstructions for controlling temperatures, flow rates of gases andliquids, chamber pressure, substrate temperature, timing of variousoperations, and other parameters of a particular process. Other computerprograms stored on memory devices associated with the controller may beemployed in some embodiments.

The computer program code for controlling the processes in a processsequence can be written in any conventional computer readableprogramming language: for example, assembly language, C, C++, Pascal,Fortran or others. Compiled object code or script is executed by theprocessor to perform the tasks identified in the program. The systemsoftware may be designed or configured in many different ways. Forexample, various chamber component subroutines or control objects may bewritten to control operation of the chamber components necessary tocarry out the described processes. Examples of programs or sections ofprograms for this purpose include process gas control code, pressurecontrol code, and plasma control code.

The controller parameters relate to process conditions that are providedto the user in the form of a recipe, and may be entered utilizing theuser interface. Signals for monitoring the process may be provided byanalog and/or digital input connections of the system controller 722.The signals for controlling the process are output on the analog anddigital output connections of the apparatus 700.

An apparatus 700 may be a multi-station or a single-station apparatus.In a multi-station configuration, the chamber 718 may have a number ofstations, for example, two stations, three stations, four stations, fivestations, six stations, seven stations, eight stations, ten stations, orany other number of stations. This number is usually determined bycomplexity of the overall process and/or ability of different operationsto share the same environment. In certain embodiments, two or morestations in a multi-station apparatus are exposed to the same processingenvironment (e.g., pressure). However, each station may have individuallocal plasma and/or heating conditions achieved by a dedicated plasmagenerator and heated pedestal.

In certain embodiments, an apparatus 700 may be a part of amulti-chamber system. For example, a system may have two, three, or evenfour separate chambers with one or more stations in each chamber. Eachchamber may have one or more corresponding transfer ports (e.g.,load-locks) in order to independently control internal environments ineach chamber.

CONCLUSION

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing the processes, systems and apparatus of the presentinvention. Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein.

What is claimed is:
 1. A temperature controlled showerhead assembly foruse in a chemical vapor deposition (CVD) apparatus, the temperaturecontrolled showerhead assembly comprising: a heat conductive stem,wherein the heat conductive stem comprises: a heat exchanger; areplaceable heating element; a seat configured to receive the heatexchanger, the heat exchanger positioned on the seat and thermallycoupled to the heat conductive stem; and an opening configured toreceive the replaceable heating element, the replaceable heating elementthermally coupled to the heat conductive stem; a back plate attached tothe heat conductive stem; a face plate thermally coupled to the heatconductive stem and attached to the back plate, the back plate includingthree or more stacked substantially solid disks decreasing in diameterfrom the attachment at the face plate to the attachment at the heatconductive stem, wherein the disk at the attachment at the face plate isconfigured to distribute a flow of gas to the face plate; and atemperature sensor thermally coupled to the face plate, wherein thetemperature controlled showerhead is configured to maintain thetemperature of the face plate within a predetermined range by providingheat transfer paths between the heating element and the face plate andbetween the heat exchanger and the face plate.
 2. The temperaturecontrolled showerhead assembly of claim 1, wherein a solid cross-sectionof the heat conductive stem is at least about 5 square inches on averagealong the length of the shaft portion.
 3. The temperature controlledshowerhead assembly of claim 1, wherein one or more components selectedfrom the group consisting of the heat conductive stem, the back plate,and the face plate comprising a material with a thermal conductivity ofat least about 150 Watts per meter per Kelvin.
 4. The temperaturecontrolled showerhead assembly of claim 1, wherein one or morecomponents selected from the group consisting of the heat conductivestem, the back plate, and the face plate comprising a material selectedfrom the group consisting of aluminum 6061 and aluminum
 3003. 5. Thetemperature controlled showerhead assembly of claim 1, wherein anaverage thickness of the back plate is at least about 2 inches.
 6. Thetemperature controlled showerhead assembly of claim 1, wherein anaverage thickness of the face plate is between about 0.5 inches and 1inch.
 7. The temperature controlled showerhead assembly of claim 1,wherein an average gap between the face plate and the back plate isbetween about 0.25 inch and 0.75 inch.
 8. The temperature controlledshowerhead assembly of claim 1, wherein a contact area between the faceplate and the back plate is between about 30 square inches and 50 squareinches.
 9. The temperature controlled showerhead assembly of claim 1,wherein the face plate has a diameter of between about 13.5 inches and16.5 inches.
 10. The temperature controlled showerhead assembly of claim1, wherein the heat exchanger comprises a convective cooling fluidpassageway configured to allow for a flow of a cooling fluid.
 11. Thetemperature controlled showerhead assembly of claim 10, wherein thecooling fluid is selected from the group consisting of water and aliquid antifreeze solution.
 12. The temperature controlled showerheadassembly of claim 1, wherein the heat exchanger is positioned withinabout 7 inches from the face plate.
 13. The temperature controlledshowerhead assembly of claim 1, wherein the temperature controlledshowerhead assembly is configured to maintain the temperature of theface plate at between about 200° C. and 300° C. for an emissivity of theface plate at between about 0.2 and 0.8.
 14. The temperature controlledshowerhead assembly of claim 1, wherein the heating element comprisestwo cartridge heaters each configured to provide power output of atleast about 500 W.
 15. The temperature controlled showerhead assembly ofclaim 1, wherein the stem comprises a top surface and wherein theopening is at the top surface of the stem.
 16. The temperaturecontrolled showerhead assembly of claim 1, wherein the stem comprises atop surface and wherein the temperature sensor is positioned within thestem and configured to be placed into the stem and removed from the stemthrough the top surface.
 17. The temperature controlled showerheadassembly of claim 1, wherein an external surface of one or more elementsselected from the group consisting of the stem and the back platecomprises a high emissivity surface.
 18. The temperature controlledshowerhead assembly of claim 17, wherein the high emissivity surface isanodized aluminum.
 19. The temperature controlled showerhead assembly ofclaim 1, wherein the face plate has a plurality of through holesconfigured for uniform distribution of process gases.
 20. Thetemperature controlled showerhead assembly of claim 1, wherein the heatexchanger is removably mounted on the seat of the heat conductive stemof the temperature controlled showerhead assembly.
 21. The temperaturecontrolled showerhead assembly of claim 1, wherein the temperaturesensor is removable from the temperature controlled showerhead assembly.22. The temperature controlled showerhead assembly of claim 1, whereinthe back plate and the face plate are integrated together to form asingle unified body.
 23. The temperature controlled showerhead assemblyof claim 1, wherein each of the stacked disks has a different thickness.24. The temperature controlled showerhead assembly of claim 1, whereinthe disk at the attachment at the face plate is configured to distributethe flow of gas to a gap between the back plate and the face plate. 25.A temperature controlled showerhead assembly for use in a chemical vapordeposition (CVD) apparatus, the temperature controlled showerheadassembly comprising: a heat conductive stem comprising aluminum 6061,wherein the heat conductive stem further comprises: a heater exchanger;one or more cartridge heaters; a seat configured to receive the heatexchanger, the heat exchanger positioned on the seat and thermallycoupled to the heat conductive stem; and an opening configured toreceive the one or more cartridge heaters, each cartridge heaterconfigured to provide power output of at least about 500 W, the one ormore cartridge heaters thermally coupled to the heat conductive stem; aback plate comprising aluminum 6061 and having an average thickness ofat least about 2 inches, wherein the back plate is attached to the heatconductive stem; a face plate comprising aluminum 6061 and having anaverage thickness of between about 0.5 inches and 1 inch, wherein theface plate is thermally coupled to the heat conductive stem and attachedto the back plate with an average gap between the face plate and theback plate of between about 0.25 inch and 0.75 inch, the back plateincluding three or more stacked substantially solid disks decreasing indiameter from the attachment at the face plate to the attachment at theheat conductive stem, wherein the disk at the attachment at the faceplate is configured to distribute a flow of gas to the gap between theface plate and the backplate; and a temperature sensor thermally coupledto the face plate, wherein the temperature controlled showerhead isconfigured to maintain the temperature of the face plate within apredetermined range by providing heat transfer paths between the heatingelement and the face plate and between the heat exchanger and the faceplate.
 26. A Chemical Vapor Deposition (CVD) system for depositing asemiconductor material on a partially manufactured semiconductorsubstrate, the CVD system comprising: a processing chamber configured tomaintain a low pressure environment within the processing chamber; asubstrate support for holding the partially manufactured semiconductorsubstrate and maintaining a temperature of the partially manufacturedsemiconductor substrate at between about 500° C. and 600° C.; atemperature controlled showerhead assembly comprising: a heat conductivestem, wherein the heat conductive stem comprises: a heat exchanger; areplaceable heating element; a seat configured to receive the heatexchanger, the heat exchanger positioned on the seat and thermallycoupled to the heat conductive stem; and an opening configured toreceive the replaceable heating element, the replaceable heating elementthermally coupled to the heat conductive stem; a back plate attached tothe heat conductive stem; a face plate thermally coupled to the heatconductive stem and attached to the back plate, the back plate includingthree or more stacked substantially solid disks decreasing in diameterfrom the attachment at the face plate to the attachment at the heatconductive stem, wherein the disk at the attachment at the face plate isconfigured to distribute a flow of gas to the face plate; and atemperature sensor thermally coupled to the face plate, wherein thetemperature controlled showerhead is configured to maintain thetemperature of the face plate within a predetermined range by providingheat transfer paths between the heating element and the face plate andbetween the heat exchanger and the face plate.
 27. The CVD system ofclaim 26, wherein the face plate of the temperature controlledshowerhead is positioned within about 0.7 inches from the substratesupport and wherein the temperature controlled showerhead is configuredto maintain the temperature of the face plate at between about 200° C.and 300° C. while the substrate support is maintained at between about500° C. and 550° C.
 28. The CVD system of claim 26, further comprisingan in-situ plasma generator.
 29. The CVD system of claim 26, wherein theCVD system is a single-station deposition system.
 30. The CVD system ofclaim 26, further comprising a second substrate support.
 31. The CVDsystem of claim 30, wherein the substrate support and the secondsubstrate support are positioned inside the processing chamber and areconfigured to be exposed to the same low pressure environment.
 32. TheCVD system of claim 30, further comprising a second processing chamberconfigured to maintain a different environment than the processingchamber, wherein the substrate support is positioned in the processingchamber and the second substrate support is positioned in the secondprocessing chamber.
 33. The CVD system of claim 26, wherein the backplate and the face plate are integrated together to form a singleunified body.
 34. The temperature controlled showerhead assembly ofclaim 26, wherein the disk at the attachment at the face plate isconfigured to distribute the flow of gas to a gap between the back plateand the face plate.